U.S. patent application number 13/227711 was filed with the patent office on 2012-03-08 for blow molding process, apparatus and article.
This patent application is currently assigned to Salflex Polymers Ltd.. Invention is credited to Dale Escue, William Matthew Foster, Daniel Hall, Dan Lockstadt.
Application Number | 20120056356 13/227711 |
Document ID | / |
Family ID | 45770122 |
Filed Date | 2012-03-08 |
United States Patent
Application |
20120056356 |
Kind Code |
A1 |
Hall; Daniel ; et
al. |
March 8, 2012 |
Blow Molding Process, Apparatus and Article
Abstract
Provided is a process for producing a hollow article provided
with an internal component. The process comprises providing a
molding station having first and second mold portions together
defining a mold cavity. A parison having a top and bottom end is
then positioned within the molding station. Using a carrier, at
least one component mounted on the carrier is inserted into the
parison through the top end of the parison. The parison is then
pressed against the component using displaceable mold cores
provided in each of first and second mold portions, after which the
carrier is removed from the molding station. The top and bottom
ends of the parison are sealed, and the molding station is closed.
Blow molding pressure is applied to the parison to urge the parison
against the contours of the mold cavity, after which the molding
station is opened and the formed hollow article is removed.
Inventors: |
Hall; Daniel; (Smyrna,
TN) ; Foster; William Matthew; (White House, TN)
; Lockstadt; Dan; (Castalian Springs, TN) ; Escue;
Dale; (Portland, TN) |
Assignee: |
Salflex Polymers Ltd.
Weston
CA
|
Family ID: |
45770122 |
Appl. No.: |
13/227711 |
Filed: |
September 8, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61380935 |
Sep 8, 2010 |
|
|
|
Current U.S.
Class: |
264/533 ;
264/531; 425/541 |
Current CPC
Class: |
B29K 2023/065 20130101;
B29C 49/4815 20130101; B29K 2023/12 20130101; B29K 2027/12
20130101; B29C 49/04 20130101; B29C 49/20 20130101; B29C 49/4247
20130101; B29C 49/22 20130101; B29K 2067/00 20130101; B29K 2023/086
20130101; B29K 2081/04 20130101; B29L 2031/7172 20130101; B29K
2077/00 20130101 |
Class at
Publication: |
264/533 ;
264/531; 425/541 |
International
Class: |
B29C 49/04 20060101
B29C049/04; B29C 49/32 20060101 B29C049/32 |
Claims
1. A process for producing a hollow article provided with internal
components, the process comprising: providing a molding station
having first and second mold portions together defining a mold
cavity, positioning within said molding station a parison having a
top end and a bottom end, inserting through said top end of said
parison a carrier having positioned thereon at least one component
to be inserted into said parison, pressing said parison against
said component using displaceable mold cores provided in each of
said first and second mold portions, removing said carrier from
said molding station, sealing said top and bottom ends of said
parison, closing said molding station, applying blow molding
pressure to said parison to urge said parison against the contour
of said mold cavity, and opening said molding station and removing
the formed hollow article.
2. The process according to claim 1, wherein said parison is
extruded from an extrusion head, cut to a predetermined length, and
transported to said molding station using a conveying device.
3. The process according to claim 1, further comprising opening
said top end of said parison to facilitate the insertion of said
carrier and component mounted thereon.
4. The process according to claim 3, wherein said top end of said
parison is opened using a stretcher mechanism.
5. The process according to claim 1, further comprising partially
closing said first and second mold portions prior to pressing said
parison against said component using said displaceable mold
cores.
6. The process according to claim 1, further comprising subjecting
the closed preform to a pre-blow pressure prior to closing said
molding station.
7. The process according to claim 1, further comprising inserting
through said bottom end of said parison a second carrier having
positioned thereon at least one component to be inserted into said
parison.
8. The process according to claim 7, further comprising opening
said bottom end of said parison to facilitate the insertion of said
second carrier and component mounted thereon.
9. A blow molding apparatus for producing a hollow article provided
with internal components, comprising, a blow molding station having
first and second mold portions together defining a mold cavity,
said blow molding station being configured to receive a parison, a
carrier positioned to deliver a component through a top end of said
parison located in said blow molding station, at least one
displaceable mold core in each of said first and second mold
portions, said displaceable mold core being configured to engage
said parison to urge localized contact between said parison and
said component, and a set of sliding pinch plates operably disposed
above and below said first and second mold portions to seal said
top and bottom ends, respectively.
10. The apparatus according to claim 9, further comprising a
conveying device to receive and transport said parison from an
extrusion head to said molding station.
11. The apparatus according to claim 10, wherein said conveying
device is configured to engage an outside surface of said
parison.
12. The apparatus according to claim 11, wherein said conveying
device comprises a gripper assembly having a segmented vacuum ring
configured to engage said outside surface of said parison.
13. The apparatus according to claim 10, further comprising a
stretcher mechanism provided on said conveying device, said
stretcher mechanism having a plurality of stretch rods arranged to
engage and inside surface of said parison, said stretch rods being
radially movable to outwardly stretch said top end of said
parison.
14. The apparatus according to claim 13, wherein said stretcher
mechanism comprises between 6 to 8 stretch rods arranged in annular
series about said parison.
15. The apparatus according to claim 9, wherein each of said at
least one displaceable mold cores is coupled to a respective
actuator.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a non-provisional application claiming priority
under 35 USC .sctn.119 to U.S. Provisional Patent Application Ser.
No. 61/380,935 filed on Sep. 8, 2010.
FIELD OF THE INVENTION
[0002] The present invention relates to the production of hollow
plastic articles, and in particular to a method and an apparatus
for the blow-molding of hollow plastic articles with inserted
components.
BACKGROUND OF THE INVENTION
[0003] Blow moulded hollow articles can be made by the blow molding
process. This is a common technique to make hollow articles such as
fuel tanks or portable transport containers. The disadvantage of
this polymer processing method is that that the integration of
components inside the hollow plastic article after molding is very
difficult and limited. For example, for fuel tanks components can
be added after molding by inserting them through cut holes. These
holes are subsequently covered by caps or with fuel tank components
leaving an additional permeation path for fuel vapor permeation
from the inside to the outside.
[0004] Another process known in the prior art is a twin-sheet
forming process. Two half-shells are formed from sheets and welded
together in a second step. It is possible to insert components
between two half-shells before they are welded. A disadvantage of
this thermoforming process over blow moulding is that the thickness
of the extruded sheet is uniform resulting in uneven thinning in
the finished part in high blow ratio areas. Another disadvantage is
that there is an additional time and energy required to heat up the
two-shells in order to be able to weld the shells.
[0005] Another process for producing hollow plastic articles is a
twin-sheet, blow moulding process. The process encompasses forming
a hollow parison with a blow moulding extrusion apparatus,
splitting the parison into two sheets, thermoforming the sheets to
form half-shells and then welding the shells together. Components
may be added between the half-shells before the welding process.
The disadvantage of this process is that a capital investment is
required for parison splitting and twin sheet handling devices with
poorer productivity arising from operating, maintaining and
cleaning the additional devices.
SUMMARY OF THE INVENTION
[0006] According to an aspect of an embodiment provided is a
process for producing a hollow article provided with an internal
component. The process comprises providing a molding station having
first and second mold portions together defining a mold cavity. A
parison having a top and bottom end is then positioned within the
molding station. Using a carrier, at least one component mounted on
the carrier is inserted into the parison through the top end of the
parison. The parison is then pressed against the component using
displaceable mold cores provided in each of the first and second
mold portions, after which the carrier is removed from the molding
station. The top and bottom ends of the parison are sealed, and the
molding station is closed. Blow molding pressure is applied to the
parison to urge the parison against the contours of the mold
cavity, after which the molding station is opened and the formed
hollow article is removed.
[0007] According to another aspect of an embodiment, provided is a
blow molding apparatus for producing a hollow article provided with
an internal component. The blow molding apparatus comprises a blow
molding station having a first and second mold portion that
together define a mold cavity, the blow molding station being
configured to receive a parison. A carrier is positioned to deliver
a component through a top end of the parison located in the blow
molding station. Each of the first and second mold portions
provides at least one displaceable mold core configured to engage
the parison to urge localized contact between the parison and the
component. A set of sliding pinch plates operably disposed above
and below the first and second mold portions are also provided to
seal the top and bottom ends, respectively.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The foregoing and other features and advantages of the
invention will be apparent from the following description of the
invention as illustrated in the accompanying drawings. The
accompanying drawings, which are incorporated herein and form a
part of the specification, further serve to explain the principles
of the invention and to enable a person skilled in the pertinent
art to make and use the invention. The drawings are not to
scale.
[0009] FIG. 1 shows diagrammatically in cross-section the step of
parison extrusion from an extruder.
[0010] FIG. 2 shows diagrammatically in cross-section the use of
conveying device to transport a parison, according to the present
invention.
[0011] FIG. 3 shows diagrammatically in cross-section the
positioning of a parison within a blow molding station, according
to the present invention.
[0012] FIGS. 4 and 5 shows diagrammatically in cross-section the
use of a stretcher mechanism to widen the open top end of parison,
according to the present invention.
[0013] FIG. 6 shows diagrammatically in cross-section the insertion
of a component on a carrier within the parison in the blow molding
station from the top of the machine, according to the present
invention.
[0014] FIG. 7 shows diagrammatically in cross-section the extension
of mold cores into the mold cavity to engage the parison and weld
the component in position, according to the present invention.
[0015] FIG. 8 shows diagrammatically in cross-section the closure
of pinch plates on the top and bottom ends of the parison to create
a sealed internal chamber, according to the present invention.
[0016] FIG. 9 shows diagrammatically in cross-section the closure
of the first and second mold portions to establish the final shape
of the mold cavity, according to the present invention.
[0017] FIG. 10 shows diagrammatically in cross-section the parison
in the mold cavity on being blow molded, according to the present
invention.
[0018] FIG. 11 shows diagrammatically in cross-section the opening
of the first and second mold portions to release the finished
molded article, according to the present invention.
[0019] FIG. 12 shows diagrammatically in cross-section the
insertion of a component on a carrier through the top end of the
parison, and the insertion of a second component on a second
carrier through the bottom end of the parison, according to an
alternate embodiment of the present invention.
DESCRIPTION OF PREFERRED EMBODIMENT
[0020] Specific embodiments of the present invention will now be
described with reference to the figures. The following detailed
description is merely exemplary in nature and is not intended to
limit the invention or the application and uses of the invention. A
person skilled in the relevant art will recognize that other
configurations and arrangements can be used without departing from
the scope of the invention. Although the description of the
embodiments hereof is in the context of blow molding containers
having inserted components, the invention may also be used in other
blow molding arrangements. Furthermore, there is no intention to be
bound by any expressed or implied theory presented in the preceding
technical field, background, brief summary or the following
detailed description.
[0021] Presented diagrammatically in FIG. 1 is a cross-sectional
view of an extrusion head 12 which operates to extrude a hollow
tube-like segment of thermoplastic material generally referred to
as a hollow parison 14. As shown in FIG. 2, after a predetermined
length or segment of material has been extruded, parison 14 is
taken hold by a suitable conveying device 16 and cut.
[0022] An exemplary conveying device 16 is a robotic assembly
system 18 fitted with end-of-arm tooling suitable for handling a
parison, for example a gripper assembly 20. A variety of
configurations are possible for gripper assembly 20. Functionally,
gripper assembly 20 is configured to grasp and release the top end
22 of parison 14 to permit for parison transport and control.
Gripper assembly 20 may be attached to an extendible support 24
forming part of the robotic assembly system.
[0023] In one exemplary embodiment, robotic assembly system 18 is a
6-axis robot having an end-of-arm gripper assembly 20 comprised of
a segmented vacuum ring 26 configured to contact and engage the
outside surface of parison 14. As shown, segmented vacuum ring 26
is comprised of a plurality of vacuum units 28 that in total form a
ring-like structure around top end 22 of parison 14. Each vacuum
unit 28 is configured to move radially relative to axis A, so as to
permit segmented vacuum ring 26 to open and close during initial
engagement with parison 14. By virtue of gripper assembly 20
engaging and retaining parison 14 on the outside surface 30,
parison 14 retains the tube-like hollow structure at top end 22. As
such, gripper assembly 20 presents a central aperture 32 generally
of similar diameter to parison 14, aperture 32 permitting for
passage of components to be inserted in parison 14, as will be
described below.
[0024] While gripper assembly 20 detailed above maintains parison
14 in a substantially circular ring-like configuration, alternate
arrangements of the segmented units of gripper assembly are
possible, such as to maintain top end 22 of parison 14 in a
polygonal (e.g. hexagonal), square or non-circular shape.
[0025] On grasping and retaining parison 14, conveying device 16
removes parison 14 from extrusion head 12, and delivers it to a
blow molding station 34, as shown for example in FIG. 3.
Blow-molding station 34 provides a mold cavity 36 shaped to form
the desired hollow article, mold cavity 36 generally being defined
by a first mold portion 38 and a second mold portion 40. First and
second mold portions 38, 40 are movable to open/close mold cavity
36, enabling the loading of parison 14 at the beginning of a mold
cycle, and the unloading of the finished hollow article at the end
of the mold cycle.
[0026] Components to be inserted into parison 14 prior to
blow-molding are inserted through top end 22. To facilitate the
insertion of larger components into parison 14, as shown in FIGS. 4
and 5, top end 22 of parison 14 may be stretched to increase the
overall opening relative to the original diameter. To achieve this,
each vacuum unit 28 of gripper assembly 20 may be displaced
outwardly relative to axis A, so as to promote the opening of top
end 22. In addition, to provide additional stretching force on
parison 14, conveying device 16 may further include a stretcher
mechanism comprising a plurality of stretch rods or fingers 42 to
engage the inside surface 44 of parison 14. The plurality of
stretch rods 42 are arranged in an annular series relative to axis
A of parison 14. To promote the opening of top end 22, at least 3
stretch rods are required, but it will be appreciated that a
greater number of stretch rods 42 may be advantageously used to
reduce localized stresses during opening. For example, in one
embodiment, 6 to 8 stretch rods 42 may be used. Regardless of the
number of stretch rods 42 used, stretch rods 42 are equally spaced
about axis A. Functionally, stretch rods 42 are movable from a
normal rest position corresponding to the original size of top end
22 (as shown in FIG. 4) to an extended position in which stretch
rods 42 have been moved radially outward to expand top end 20 of
parison 14 (as shown in FIG. 5). As top end 22 is retained on
outside surface 30 by gripper assembly 20, the radial displacement
of the stretch rods 42 is matched to and coordinated with the
radial displacement of the vacuum units 28 defining gripper
assembly 20.
[0027] While parison 14 may be symmetrically stretched, that is
each point on top end 22 being displaced by the same radial extent,
it is not necessary for this to occur. In some embodiments, through
the action of the matched stretch rods 42 and vacuum units 28,
points about top end 22 of parison 14 may be moved to different
radial extents to achieve a certain shaped opening. As such, the
manipulation of top end 22, in particular of the opening may be
either symmetrical or non-symmetrical depending on the desired
shape to be achieved.
[0028] In some embodiments, to ensure engagement between stretch
rods 42 and parison 14, stretch rods 42 may be provided with
offsets (not shown). Offsets serve to securely engage inside
surface 44 of parison 14 to assist in preventing parison 14 from
dropping under weight/gravity. Alternatively, stretch rods 42 may
incorporate gripping features that include mechanical or vacuum
based engagement with inside surface 44 of parison 14.
[0029] Turning now to FIG. 6, with parison 14 positioned within
blow molding station 34, and top end 22 expanded to present an
enlarged opening, a component 46 is inserted into parison 14. To
achieve this, component 46 is mounted on a suitable carrier 48
configured to deliver component 46 to a predetermined position
inside parison 14 (shown in dot). Carrier 48 and component 46 are
inserted through aperture 32 provided on gripper assembly 20.
[0030] Each of first and second mold portions 38, 40 provide at
least one respective movable mold core 50, 52 that are displaceable
relative to mold cavity 26. As such, mold cores 50, 52 are
configured to protrude and retract from mold cavity 36, so as to
engage/disengage from parison 14. To facilitate movement, mold
cores 50, 52 may be coupled to a respective actuator 54, 56 capable
of lateral displacement. As will be appreciated, the stroke
provided by actuator 54, 56 may be adjustable to allow for accurate
positioning of end surface 58 of mold cores 54, 56 relative to the
fully extended and fully retracted positions. For example, in the
retracted position, end surface 58 may be partially protruding,
flush, or partially recessed relative to inside surface 60 of mold
cavity 36. It will be further appreciated that while a single
actuator may be used to control the movement of mold core 50, 52,
in some embodiments, particularly where a plurality of mold cores
are provided, a yoke plate configuration (not shown) may be
implemented.
[0031] Turning now to FIG. 7, with component 46 positioned within
parison 14, mold cores 50, 52 in each of first and second mold
portions 38, 40 are extended into mold cavity 36, thereby engaging
parison 14. As the walls of parison 14 are locally pushed inwardly
by mold cores 50, 52, thus forming protrusions 62, 64, they are
urged into contact with component 46, resulting in a permanent bond
or weld to maintain component 46 in position. Once the points of
contact are established, carrier 48 is detached from component 46
and withdrawn from mold cavity 36.
[0032] In some embodiments, prior to extending mold cores 50, 52
into mold cavity 36, first and second mold portions 38, 40 may be
partially closed to an intermediate position.
[0033] As shown in FIG. 8, the bottom end 66 of parison 14 is
sealed using a first set of sliding pinch plates 68a/68b operably
disposed below first and second mold portions 38, 40. Sliding pinch
plates 68a/68b are configured to slide towards each other, thereby
effecting closure of the distal end of parison 14. Similarly, top
end 22 of parison 14 is sealed using a second set of sliding pinch
plates 70a/70b disposed below the stretcher mechanism. While the
first and second sets of sliding pinch plates 68a/68b, 70a/70b] may
be integrated into the gripper assembly 20 structure, the pinch
plates may alternatively be part of a separate pre-blow assembly
that is moved into position, for example through the use of a
robot.
[0034] Parison 14 is subject to a pre-blow pressure by way of
pressurized gas (e.g. air) introduced through one or more blow
needles/pins (not shown) in fluid communication with the internal
chamber formed within the sealed parison 14.
[0035] As shown in FIG. 9, first and second mold portions 38, 40
are then closed, with mold cores 50, 52 being retracted to
disengage parison 14. Mold cores 50, 52 are retracted sufficiently
to position end surface 58 at a location to achieve the desired end
feature in the finished article. In the embodiment shown, mold
cores 50, 52 are retracted sufficiently to position end surface 58
at a location flush with the inside surface 60 of mold cavity 36,
so as to minimize surface markings on the finished article. With
first and second mold portions 38, 40 fully closed, blow molding
pressure is applied through the one or more blow needles/pins (not
shown). As such, parison 14 is caused to bear completely against
the contour of mold cavity 48, thus forming the final hollow
article 72, shown in FIG. 10.
[0036] As shown in FIG. 11, on completion of the blow molding step
and cooling period, first and second mold portions 38, 40 are
opened, and the resulting hollow article 72 is removed and
subjected to any required post-mold processing to remove flashing
74 or other waste material. The finished hollow article 72
comprises inserted component 46 in permanent welded contact with
the inside surface.
[0037] While parison 14 is subject to a pre-blow step prior to full
blow molding, in some embodiments, the pre-blow step may be
excluded.
[0038] While sliding pinch plates 68a/68b, 70a/70b are shown to
effect a substantially complete closure of the end regions of
parison 14, one or both sets of sliding pinch plates 68a/68b,
70a/70b may also be configured to bear against plug members
inserted within the top and/or bottom portions of parison 14. As
such, pinch plates 68a/68b, 70a/70b would inwardly displace and
bear against the plug members, allowing for a pre-blow
pressurization, subsequent to which first and second mold portions
38, 40 would be fully closed to permit for blow molding under full
blow molding pressure.
[0039] While component 46 may be permanently welded to a generally
planar region of the inside surface of finished article, it may
also be positioned to permanently weld to a protrusion or generally
non-planar region.
[0040] While the above discussion presents mold cavity 36 as being
defined by first and second mold portions 38, 40 in some
embodiments mold cavity 36 may be defined by a greater number of
mold portions.
[0041] While the above discussion presents a blow molding
arrangement wherein a single component 46 is inserted through top
end 22 of parison 14, carrier 48 may be configured to deliver a
plurality of components 46 through top end 22. Alternatively,
multiple carriers 48 may be used to position one or more components
through top end 22.
[0042] In still further embodiments, the above arrangement of
delivering a component through top end 22 of parison 14 may be
combined with a conventional bottom-load arrangement, for example
as shown in FIG. 12. As shown, two components 46/46' are inserted
into parison 14. Component 46 is inserted through top end 22 as
previously described. Component 46' is inserted through bottom end
66, where bottom end 66 is opened using a stretcher mechanism.
Similar to that used for opening top end 22, the stretcher
mechanism used on bottom end 66 may comprise a plurality of stretch
rods 42' arranged in an annular series relative to axis A of
parison 14. While at least 3 stretch rods are required, it will be
appreciated that a greater number of stretch rods 42' may be
advantageously used to reduce localized stresses during opening.
For example, in one embodiment, 6 to 8 stretch rods 42' may be
used. Regardless of the number of stretch rods 42' used, stretch
rods 42' are equally spaced about axis A. Functionally, stretch
rods 42' are movable from a normal rest position corresponding to
the original size of bottom end 66 of parison 14, to an extended
position in which stretch rods 42' have been moved radially outward
to expand bottom end 66 of parison 14 (as shown in FIG. 12). As
such, a carrier 48' can be inserted into bottom end 66 to deliver
component 46' to a predetermined positioned inside parison 14. Mold
cores 50', 52' operate similar to previously described mold cores
50, 52 to engage/disengage from parison 14, with the purpose of
urging parison 14 into contact with component 46'. The remaining
processing steps to form the final hollow article are similar to
those previously described and shown in FIGS. 7 through 11.
[0043] In still further embodiments, multiple carriers, that is
both top and bottom insertion carriers may be used to position a
single component (e.g. a fuel tank baffle) in a parison. For
example, each of the top and bottom carriers may present a portion
of a component that upon insertion and final positioning, the
portions together form a single assembled component within the
parison. In still further arrangements, a component may be inserted
via either the top or bottom carrier, with the other opposing
carrier providing guidance means during subsequent engagement by
the parison.
[0044] A variety of hollow articles can be manufactured by means of
the process described above. One application of the method is in
the production of a fuel tank used for motor vehicles. The hollow
article can also be used as a fuel tank for off road vehicles,
marine vessels, lawn and garden devices and power tools. The method
can also be used for the manufacture of containers to store and
transport fuel, liquids or chemicals.
[0045] The internal component of the hollow article may be a
structural element to reduce deformation of the hollow article upon
pressurization above ambient external pressure. In other
embodiments, the internal component may be a wave management member
(e.g. baffle) to reduce propagated sloshing noise from a liquid
filled hollow article, such as a fuel tank. In still further
embodiments, particularly where the hollow article is a fuel tank,
the internal component may be a baffle, a structural
anti-deflection element, a valve, a pump module, a sensor/sensor
mechanism, and/or a surge chamber.
[0046] The hollow articles may be formed from a mono-layer parison
comprised of a thermoplastic material. A non-limiting example of
suitable thermoplastic material includes high density
polypropylene, propylene, polyamide, acetal, polyester,
fluoropolymer, polyphenylene sulfide, and copolymers of these
plastics.
[0047] In addition to mono-layer parisons, the hollow articles may
be made from a co-extruded or multi-layer parison comprised of
thermoplastic material. A non-limiting example of suitable
thermoplastic material includes high density polypropylene,
propylene, polyamide, acetal, polyester, fluoropolymer,
polyphenylene sulfide, and copolymers of these plastics.
[0048] The mono-layer and co-extruded/multi-layer parisons may be
formed of thermoplastic material(s) containing a barrier resin such
as SELAR.TM., or inorganic additives including minerals and
glass.
[0049] Multi-layer parisons may comprise a filled or unfilled
structural layer, generally a thermoplastic material, an adhesive
layer and a barrier layer. A non-limiting example of suitable
barrier layers includes ethylene vinyl alcohol, fluoropolymer,
polyamide, acetal, polyester polyphenylene sulfide and copolymers
thereof.
[0050] While various embodiments according to the present invention
have been described above, it should be understood that they have
been presented by way of illustration and example only, and not
limitation. It will be apparent to persons skilled in the relevant
art that various changes in form and detail can be made therein
without departing from the scope of the invention. Thus, the
breadth and scope of the present invention should not be limited by
any of the above-described exemplary embodiments, but should be
defined only in accordance with the appended claims and their
equivalents. It will also be understood that each feature of each
embodiment discussed herein, and of each reference cited herein,
can be used in combination with the features of any other
combination. All patents and publications discussed herein are
incorporated by reference herein in their entirety.
* * * * *